Magnetically operated switch



United States Patent 2,827,531 MAGNETICALLY OPERATED SWITCH Elwin J. OBrien, Whittier, Calif., assignor to North American Aviation, Inc.

Application May 31, 1955, Serial No. 512,196 7 Claims. (Cl. 200-87) This invention relates to magnetically operated switches and particularly, though not exclusively, to a switch actuated magnetically in response to the rotation of a shaft member.

In the past, various switches have been constructed which are responsive to the angular rotation of a shaft. The switches are frequently utilized in conjunction with a tachometer circuit to measure the speed of rotation of a shaft. These switches have usually been either cam actuated or have utilized sliding contacts on slip rings to open and close an electric circuit. Switches of these types not only impose undesired resistive torques on the shaft but, further, are frequently subjected to what is called contact bounce. This contact bounce is particularly noticeable when a cam actuated switch is utilized with a shaft rotating at a high angular velocity. Due to the resilience of the contacts, spurious undesired openings or closings of the switch occur. Thus, if the shaft is rotating at a speed of 18,000 R. P. M., for example, considerable unreliability is present when using the above-mentioned switches.

It is therefore an object of this invention to provide an improved magnetically operated switch, which is opened and closed solely in response to magnetic forces.

It is a further object of this invention to provide in combination with a rotating shaft, means for bidirectional moving a plug of magnetic material by selectively varying the effective lengths of the air gaps between said plug and permanent magnets located opposite either end of said plug.

Other objects of invention will become apparent from the following description taken in connection with the accompanying drawings, in which:

Fig. 1 is a section view of an embodiment of the magnetically operated switch contemplated by this invention;

Fig. 2 is a section view of an alternative embodiment of the magnetically operated switch contemplated by this invention utilized in conjunction with a rotating shaft; and e Fig. 3 is a section view of the apparatus of Fig. 2 taken along the line 3-3.

Referring now to Fig. 1, plug 1 is constructed of a ferromagnetic material such as soft iron. Plug 1 is adapted to move axially within hole 2 of stationary support 3. Plates 4 and 5 are coupled together to move in synchronism between the ends of plug 1 and pole faces 6 and 7, respectively, of support 3. Plates 4 and 5 are constructed of alternate sections of ferromagnetic material and nonferromagnetic material. Although the sections of plates 4 and 5 are similar in shape and length, corresponding sections are constructed of complementary material. Thus, while sections 8 and 9 of plate 4 are made of a ferromagnetic material, sections 10 and 11 of plate 5 are made of a suitable nonmagnetic material such as brass. Similarly, sections 12 and 13 of plate 4 are made of nonmagnetic material, while corresponding sections 14 and 15 of plate 5 are made of a ferromagnetic substance. Support 3 is preferably constructed with a pair of per- 2,827,53l Patented Mar. 18, 1958 manent magnets which serve as sources of magnetic flux spaced a predetermined distance from each end of plug 1. Thus, magnetic lines of force leave north magnetic pole 16 of support 3, pass through nonmagnetic section 12 of plate 4, enter the upper end of plug 1, and pass through plug 1 to the south magnetic pole in center section 17 of support 3. Similarly, magnetic lines of force leave north magnetic pole 18 of support 3, pass through magnetic section 14 of plate 5, enter the lower end of plug 1, and

pass through plug 1 to the south magnetic pole in center section 17 of support 3.

Since section 14 of plate 5 is constructed of a ferromagnetic material such as soft iron, whereas section 12 of plate 4 is constructed of a nonmagnetic material such as brass, the reluctance of the gap between plug 1 and pole face 7 is much less than the reluctance of the gap between plug 1 and pole face 6. Therefore, the field from magnet pole 18 is appreciably stronger than the field from magnetic pole 16. Plug 1, being constructed of a ferromagnetic material, is attracted by the stronger field and, therefore, assumes the position shown in Fig. 1. As plates 4 and 5 are moved in synchonism is the directions shown by arrows 19, the relative reluctances of the gaps between plug 1 and pole faces 6 and 7 are reversed by the insertion of a section of magnetic material between plug 1 and face 6 and of a section of nonmagnetic material between plug 1 and pole 7. Plug 1 is thereby attracted toward pole 16 of support 3. Lips 20 and 21 are provided in hole 2 to limit the magnitude of the axial movement of plug 1.

Double-throw switch 22 is made responsive to the axial movement of plug 1. Switch 22 consists of stationary contacts 23 and 24 and movable contact 25. Contacts 23-25 are electrically insulated from support 3 and plug 1 by means of supports of suitable insulating material. Wires 26, 27 and 28 connect contacts 23, 24 and 25, respectively, to appropriate external circuitry (not shown). Movable contact 25 is made responsive to the axial movement of plug 1. The position of movable contact 25, and hence the condition of switch 22, is therefore determined by the relative position of plates 4 and 5.

Referring now to Fig. 2, a section view of a magnetically operated multiple switch responsive to the angular rotation of a shaft is shown. The actuation of plugs 30, 31, 32 and 33 is similar to that previously described with respect to Fig. 1. In this case, however, plates 34 and 35, containing sections of ferromagnetic and nonmagnetic material, are attached to and rotate with shaft 36. Suitable switches, similar to that previously described with respect to plug 1, are provided and are made responsive to the axial movement of each of plugs 30-33. Plugs 30-33 are always attracted by the stronger magnetic field. Therefore, the positions of the plugs are determined by the relative materials which are at any given instant interposed between each of the plugs and its corresponding pole faces. In the example shown in Fig. 2, sections 37-40 are constructed of magnetic material, while sections 41-44 are constructed of a nonmagnetic material.

Plates 34 and 35 are constructed with a pair of rings divided into appropriately spaced segments. Referring to Fig. 3, outer ring 45 of plate 34 is constructed with alternate segments 37, 46 and 47 of magnetic material with segments 44, 48 and 49 of nonmagnetic material. The segments of plate 35 are similar in length and position but are constructed of complementary material. Inner ring 50 of plate 34 and the corresponding inner ring of plate 35 are similarly divided into alternate magnetic and nonmagnetic sections of appropriate lengths.

It is readily apparent from the preceding description and the drawings that there is no physical contact between rotating shaft 36 and switches actuated by plugs 30-33. Further, since the plugs are not retracted by springs or 3 other resilient devices but are positively attracted in the appropriate direction by magnetic forces, the undesired contact bounce experienced with past switches at high speeds is eliminated.

Although the invention has been described and illustrated in detail, it is to be clearly understood that the same is by way of illustration and example only and is not to be taken by way of limitation, the spirit and scope of this invention being limited only by the terms of the appended claims.

I claim:

1. A magnetically actuated switch comprising a plug of magnetic material, means supporting said plug to allow bidirectional movement in an axial direction, switching means positioned to be actuated in response to the axial movement of said plug, a source of magnetic flux spaced a predetermined distance from axially opposite ends of said plug, and means selectively varying the magnetic permeability of the gaps between each end of said plug and said sources of magnetic flux.

2. A magnetically actuated switch comprising a plug of magnetic material, means supporting said plug to allow bidirectional movement in an axial direction; a pair of movable plates having magnetic and nonmagnetic sections, the magnetic sections of one of said plates being aligned in said axial direction with the nonmagnetic sections of the second of said plates; means supporting said plates in close proximity to the ends of said plug and adapted to allow movement of said plates in a direction normal to the axis of said plug; a source of magnetic flux positioned opposite respective ends of said plug and spaced from said ends by said plates; and switching means responsive to the axial movement of said plug when said plug is magnetically attracted toward the plate having a magnetic section adjacent to said plug.

3. A magnetically actuated switch sensitive to the rotation of a shaft comprising a plug of magnetic material, means supporting said plug to allow bidirectional movement in an axial direction, switching means positioned to be operated in response to the axial movement of said plug, a source of magnetic flux spaced a predetermined distance from each end of said plug, and a pair of plates operatively associated with said shaft, one of said plates having a closed ring divided into segments of magnetic and nonmagnetic material, the other of said plates having a ring including nonmagnetic and magnetic segments, each magnetic segment of said one plate being aligned in said axial direction with a nonmagnetic segment of said other plate, said plates being positioned to continuously convey said segments of said rings between each end of said plug and the corresponding source of magnetic flux.

4. A. magnetically actuated switch sensitive to the rotation of a shaft comprising a plug of magnetic material, means supporting said plug to allow bidirectional movement in an axial direction, switching means responsive to said axial movement of said plug, a plate operatively coupled with said shaft and having a plurality of magnetic and nonmagnetic segments, said plate being positioned to convey said segments in sequence past one end of said plug, a second plate operatively coupled with said shaft and having similar shaped segments with the material of said segments complementing the material in the corresponding segments of said first named plate, which are aligned therewith in said axial direction, said second named plate being positioned to convey the segments thereof in sequence past the other end of said plug, and sources of magnetic flux positioned opposite each end of said plug and spaced therefrom by said segments of said plates whereby said plug is magnetically attracted toward the plate having a segment of magnetic material adjacent to said plug.

5. A magnetically actuated switch sensitive to the rotation of a shaft comprising a plug of magnetic material, switching means responsive to axial movement of said plug, a pair of sources of magnetic flux, support means positioning said sources of magnetic flux with a pole face a predetermined distance from the ends of said plug, a pair of plates having respectively complementary and axially aligned magnetic and nonmagnetic sections, said plates being spaced a predetermined distance apart and positioned with one of said plates passing between each end of said plug and the pole face of the corresponding source of magnetic flux, and means responsive to rotation of said shaft for moving said plates relative to said plug and pole faces.

6. A magnetic drive comprising a reciprocable magnetic actuator, means for providing a pair of magnetic flux paths each of which includes said actuator, said means including means for generating in said paths a pair of substantially aligned magnetic flux components in said actuator, means for selectively varying the magnetic permeability of both of said paths to eifect variation of the relative magnitudes of said components whereby said actuator is magnetically driven in accordance with the direction of the larger of said components, and driven means responsive to movement of said actuator.

' 7. A magnetic drive comprising a plug of magnetic material, means supporting said plug for bidirectional movement, means for providing a pair of magnetic flux paths extending through said plug in the directions of movement thereof, said last mentioned means including means for generating in said paths a pair of flux components which oppose each other in said plug, means for simultaneously effecting opposite sense variations in the magnetic permeability of both said paths to change the relative magnitudes of said flux components whereby movement of said plug may be effected-in either of two opposite directions, and driven means responsive to movement of said plug.

References Cited in the file of this patent UNITED STATES PATENTS 2,543,014 Grace Feb. 27, 1951 2,548,581 Bigelow Apr. 10, 1951 2,560,814 Nilson et al. July 17, 1951 2,575,086 Atchison Nov. 13, L 51 FOREIGN PATENTS 124,041 Great Britain Ma -.12, 1919 538,409 Great Britain Aug. 1, 1941 623,014 Germany Mar. 27, 1936 699,682 Germany Dec. 4, 1940 

